Tilt mechanism for chairs and the like

ABSTRACT

1,098,809. Seats. M. P. BURKE. Oct. 17, 1966, No. 46227/66. Heading A4J. A seat 12, which is mounted on a tubular column to tilt about a pivot 50, is counterbalanced by the force of a compression spring 52, exerted through a cable 54. The seat is preferably mounted to rotate about the vertical axis of thrust bearing 38, together with sleeve 34, in which spring 52 is adjustably held between blocks 56 and 58. Steel cable 54 extends over pulley 70 and along channel 74 in sleeve 34. Screwthreads 30 are provided so that, on turning the ring 32, the column is extended telescopically to vary the height of the seat.

June 23, 1970 M. P. BURKE TILT MECHANISM FOR CHAIRS AND THE LIKE Filed Sept. 20, 1967 2 Sheets-Sheet 1 INVENTOR MAURICE P BURKE M M5 BY 777 M ATTORNEYS.

June 23, 1970 P. BURKE 3,516,636

TILT MECHANISM FOR CHAIRS AND THE LIKE F'iled Sept. 20, 1967 2 Sheets-Sheet 2 United States Patent 3,516,636 TILT MECHANISM FOR CHAIRS AND THE LIKE Maurice P. Burke, Montreal, Quebec, Canada, assignor to Brunswick Corporation, a corporation of Delaware Filed Sept. 20, 1967, Ser. No. 696,959 Int. Cl. A47c 3/00 US. Cl. 248381 11 Claims ABSTRACT OF THE DISCLOSURE This invention relates to chairs, and particularly to tilt mechanisms of the type shown and described in my prior United States Letters Patent 3,206,153, issued Sept. 14, 1965, wherein the chair seat is attached to a surbase which in turn is pivotally attached to a thrust member for tilting movement about a horizontal axis. The thrust member is supported by a bearing at the top of a hollow column or pedestal for angular movement of the thrust member and surbase substantially about the vertical axis of the column which conceals a heavy compression spring which opposes the tilting movement of the surbase. The springs axis is preferably coincident with the vertical axis of angular movement of the surbase. The horizontal pivot axis about which the surbase tilts is offset or spaced from the axis of angular movement thereof. In the present invention, a steel cable is coupled to the surbase at a point offset from the axis of the spring on the side of the column opposite the horizontal tilting axis of the chair and surbase. The steel cable passes downwardly around a pulley and then axially upwardly through the spring such that the tilting movement of the chair compresses the spring. The structure includes means for adjusting not only the spring tension, but also the height of the chair.

BACKGROUND OF THE INVENTION In the prior devices a tie rod gimbaled to the surbase extended through the compression spring and carried the seat member that compressed the spring on tilting movement of the surbase. With such structures, a person occupying the chair exerts a very considerable torque on the pivoted surbase. This must be counterbalanced by the spring. But the axis of pivotal movement of the surbase is necessarily close to the axis of the column for ease of tilting and also for esthetics and convenience. The spring exerts its force at the axis of the column, a place quite close to the axis of tilting. Consequently, the spring force must be quite large in order to achieve the requisite torque balance. A very strong spring must then be provided. Assembly of such devices is tedious; moreover such springs are costly. This invention provides a tilt mechanism in which the spring exerts its force not at the center of the column, but instead at the periphery of the column at a place opposite the tilting axis. As a result of this arrangement, a spring only half as strong as with earlier devices need be used because the spring force is applied to a lever arm about twice as long as most presently available chairs of this type.

In said prior devices, and as a consequence of the close location of the gimbal connection between the surbase and the spring, the gimbal moves in a distinct are about the tilting axis. This means that the spring force tends to reach a plateau. Consequently a type of toggle action occurs as the seat tilts to its maximum position. This detracts from the feeling and comfort of the chair. By locating the place of action of the spring laterally, this effect is minimized, and a better tilting action is obtained.

SUMMARY OF THE INVENTION The principal object of this invention is to provide a ice rtilt swivel mechanism for chairs or the like which permits the use of a relatively small spring force opposing tilting movement of the chair, thus facilitating more comfort for the occupier of the chair.

A further object of this invention is to provide a tilt mechanism of the character described in which the spring exerts its force not at the center of the chair pedestal, but instead at the periphery of the pedestal at a place opposite the horizontal tilting axis of the chair seat or surbase.

Another object of this invention is to provide a tilt mechanism of this character that incorporates means for adjusting not only the spring tension, but also the height of the chair.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of a chair incorporating the present invention;

FIGS. 2 and 3 are enlarged axial sectional views of the tilt mechanism shown in upright and tilted positions respectively; and

FIGS. 4, 5 and 6 are sectional views taken along planes corresponding to lines 4-4, 5-5 and 66 of FIG. 2.

DETAILED DESCRIPTION The chair (FIG. 1) includes a seat 12 and a support 14. The support 14 includes a surbase or flange 16 attached to the seat 12, a column or pedestal 18 and a suitable footed base 20.

The flange 16 (FIG. 2) has a central plate 22 pivotally mounted on a thrust member 24 for tilting movement of the chair. The thrust member 24 is in turn swivelly mounted on the column 18. The column 18 includes an outer tubular part 26 fastened to and projecting upwardly of the base 20, and an inner tubular part 28 threadedly connected to the outer part as at 30 for adjustment of the effective height of the column 18. The upper projecting end of the inner column part 28 carries a skirt 32 to hide the threads and to serve as a handle for adjustment of the column height.

The thrust member 24 includes a sleeve 34 and a top plate 36 that overhangs the sleeve. The overhanging part of the plate 36 rests upon a thrust bearing 38 mounted in a recess in the upper end of the skirt 32. The sleeve 34 is guided for angular movement within the inner column part 28 by spaced sleeve bearings 40 and 42. The lower bearing 42 is carried by a pulley block 44 attached to the lower end of the sleeve 34, and to be described more fully hereinafter.

The plates 22 and 36 of the surbase and the thrust member have flat surfaces normally engageable with each other to determine an upright chair position. These plates are pivoted together for tilting movement about a horizontal axis a located at the side of the thrust member. For this purpose, the surbase plate 22 has an access slot 46 (FIG. 4) that receives a hinge knuckle 48 formed on the thrust member plate 36. A pin 50 passes through the hinge knuckle 48 and is secured to seats formed in the upper surface of the surbase plate 22 located on opposite sides of the slot 44.

In order increasingly to resist tilting movement of the surbase 16, a coil spring 52 is provided that is accommodated in the sleeve 34. The spring 52 is coupled to the surbase by the aid of a steel cable 54. A cap 56 fits the upper end of the spring 52. The lower end of the spring 52 rests on a seat pad 58 that is adjustably mounted on top of the pulley block 44. For this purpose, a post 60 is mounted on the block for rotation about a vertical axis offset from the center of tht sleeve 34 by the aid of bearings 62 and 64. A flange 66 limits downward movement of the post 60. The upper end of the post 60 threadedly engages the seat pad 58. By rotating the post 60 as by a suitable tool cooperable with its accessible 3 lower end, the vertical position of the seat pad 58 is adjusted.

The cable 54 has one end attached to the cap 56 as by a suitable end fitting 68. The cable 54 then passes axially downwardly through the spring 52 and the seat pad 58 and about a pulley 70 mounted in a slot 72 in a corner of the pulley block 44. The cable then passes through the side opening of the slot 72 and upwardly along a channel 74 (see also FIGS. 5 and 6) formed along the outside of the sleeve 34. The cable 54 then passes upwardly through apertures 76 and 78 in the plates 36 and 22 where it attaches to an end fitting 80. The end fitting 80 engages a gimbal 82 accommodated in a seat 84 in the upper surface of the surbase plate 22.

The length of the cable 54 determines the position of spring cap 56 when the surbase engages the plate 36 of the thrust member. The seat pad 58 then determines the degree of compression of the spring 52 and hence the force that it normally exerts in order to counterbalance, more or less, the weight of the occupant at the full tilted position. When the seat tilts (FIG. 3) the upper end of the spring moves downwardly and the opposing torque accordingly builds up.

In assembling the mechanism, the thrust member sleeve 34 is dropped into the inner column part 28 until the plate 36 seats on the bearing 50. A nut 86 is then attached to the lower end of the pulley block and rotated until it locks against the lower edge of the inner column part. A set screw 88 holds the parts in place. The seat is accordingly held against removal from the column 18. The nut 86 has a flange 90 that opposes the lower edge of the outer column part 26 to limit the height adjustment of the column.

The spring 52 exerts its force at a place spaced from the tilting axis a near the periphery of the column and thus the lever arm is twice as long as most presently available chairs of this type, thus permitting the use of a spring only half as strong as earlier devices.

The foregoing detailed description has been given for clearness of understanding only and no unnecessary limitations should be understood therefrom as some modifications will be obvious to those skilled in the art.

The embodiments of the invention in which an exclusive property or privelege is claimed are defined as follows:

1. In a tilt mechanism for a chair: a hollow column; a thrust member supported on the column; a surbase for supporting a seat, and pivotally joined to the thrust member for movement about a horizontal axis located on one side of the column; a spring accommodated in the column; and a cable having one end connected to the surbase at a place located on the other side of the column when the surbase is in its rest position to provide a moment arm between said place and said horizontal axis at least equal to the width of said column, said cable having its other end connected to said spring whereby angular movement of said surbase about said horizontal axis away from its rest position causes the spring to store energy.

2. The tilt mechanism of claim 1 in which said spring is a coil spring with its axis substantially coinciding with that of said column, there being a pulley at the bottom of the column guiding the cable from the side of said column to the center thereof, said cable being attached to the upper end of said coil spring, the lower end of said coil spring being restrained from movement.

3. The tilt mechanism of claim 2 in which said thrust member has a sleeve guided in the column for movement about the column axis, the thrust member being supported on the column by thrust'bearing means, the lower end of said sleeve carrying a block for mounting said pulley.

4. The tilt mechanism of claim 3 in which the lower end of said coil spring is mounted on a seat pad, there being screw threaded means carried by the seat pad and the pulley block for adjusting the longitudinal position of said seat pad.

5. The tilt mechanism of claim 4 in which said screw threaded means includes a post mounted on the pulley block for angular movement about a vertical axis spaced laterally of said column axis, the lower end of said post being accessible for engagement with a tool, the upper end of said post being threaded, the said seat pad having a threaded aperture cooperating with said threaded upper end of said post.

6. The tilt mechanism of claim 1 in which said thrust member has a sleeve guided in the column for movement about the column axis, said thrust member having an overhanging plate engaging a thrust bearing mounted at the top of said column, there being a block carried at the inner end of said sleeve; said spring being a compression coil spring with its axis substantially coinciding with the axis of said column; said sleeve having a channel along its outer surface accommodating the outer run of said cable; said cable having an inner run extending from the upper end of said coil spring downwardly to the said block; a pulley mounted by said block and defining a course between the inner and outer runs of said cable.

7. The tilt mechanism of claim 6 together with a post mounted on said pulley block for angular movement about a vertical axis spaced from the axis of said column, the lower end of said post being accessible for imparting angular movement thereto, the upper end of said post being threaded, there being a seat pad for the lower end of said coil spring having a threaded aperture engaging the threaded end of said post for adjustment of the force of said coil spring.

8. The tilt mechanism of claim 7 in which said column comprises telescopic threadedly adustable inner and outer parts, the outer part being supported by a base, the thrust member being supported on the inner part.

9. The tilt mechanism of claim 8 together with a nut carried by said block and locking said thrust member to the inner column part by engagement with the lower end of said inner column part.

10. The tile mechanism of claim 9 in which said nut has a flange opposed to the lower end of said outer column part to limit upward movement of said inner column part.

11. In a tilt mechanism for a chair: means forming a hollow vertical support for said chair; a spring accommodated in said support; means mounting said chair on said hollow support for movement about a horizontal axis located on one side of said support; and a cable having one end connected to the base of said chair at a place located on the other side of the support when the surbase is in its rest position to provide a moment arm between said place and said horizontal axis at least equal to the width of said support, said cable having its other end connected to said spring whereby angular movement of said chair about said horizontal axis away from its rest position causes the spring to store energy.

References Cited UNITED STATES PATENTS 617,000 l/ 1899 Wilberforce 248-3 81 805,522 11/ 1905 Bethke 248-3 82 1,834,609 12/1931 Fitts 16-78 1,880,870 10/1932 Demo 16-78 2,398,211 4/1946 Du Pont 248-376 3,185,430 5/1965 Bernard 248-381 3,206,153 9/1965 Burke 248-388 3,220,687 11/1965 Baermann 248-378 3,220,688 11/1965 Baermann 248-3 84 3,352,526 11/ 1967 Anderson 297-304 FRANCIS K. ZUGEL, Primary Examiner US. Cl. X.R. 

